NEAR-FIELD AND FAR-FIELD PROPAGATION OF BEAMS AND PULSES IN DISPERSIVE MEDIA

We formulate an efficient exact method of propagating optical wave pac kets (and cw beams) in isotropic and nonisotropic dispersive media. Th e method does not make the slowly varying envelope approximation in ti me or space and treats dispersion and diffraction exactly to all order s, even in the near field. It can also be used to determine the partia l differential wave equation for pulses (and beams) to any order as a power series in the partial derivatives with respect to time and space . The method can treat extremely focused pulses and beams, e.g., from near-field scanning optical microscopy sources whose transverse spatia l extent in smaller than a wavelength. (C) 1997 Optical Society of Ame rica.